Electromagnetic relays



28, 1962 L. H. MAYER 3,051,804

ELECTROMAGNETIC RELAYS Filed Dec. 28. 1960 United States Patent3,051,804 ELECTROMAGNETIC RELAYS Lewis Henry Mayer, Princeton, Ind.,assignor to American Machine & Foundry Company, a corporation of NewJersey Filed Dec. 28, 1960, Ser. No. 79,064 6 Claims. (Cl. 200-87) Thisinvention relates to relays and, more particularly, to electromagneticrelays of the type having a restoring spring which, when the relay isde-energized, moves the armature to and holds it in normal position.

One of the objects of this invention is to provide an improved relaywhich is compact, efficient in operation and simple and inexpensive tomanufacture.

Another object is to provide a compact relay embodying an improved corestructure, contact assembly and spring retainer bracket.

A further object is to provide an electromagnetic relay with amulti-purpose bracket which anchors one end of the restoring spring,limits pivotal movement of the armature, prevents armature sticking andprevents the armature from being accidentally dislocated from engagementwith a fulcrum edge.

Still another object is to provide a relay, of the class described, withimproved means by which the relay can be keyed to a supporting member.

Another object is to provide an improved pole face and armaturearrangement providing a relatively great holding force regardless ofvariations in manufacturing tolerances.

In order that the manner in which these and other objects are attained,in accordance with the invention, can be understood in detail, referenceis had to the accompanying drawings, which form a part of thisspecification, and wherein:

FIG. 1 is a side elevational view of a relay constructed in accordancewith one embodiment of the invention;

FIG. 2 is an end elevational view (from the left, as viewed in FIG. 1)of the relay of FIG. 1, with parts broken away for clarity;

FIG. 3 is a top plan view (from the top, as viewed in FIG. 1) of therelay of FIG. 1;

FIG. 4 is a sectional view taken on line 4-4, FIG. 1;

FIG. 5 is a perspective view, on an enlarged scale for clarity, of abracket member employed in the relay of FIG. 1;

FIG. 6 is an elevational View, similar to FIG. 1, illustrating amodification of a portion of the relay, and

FIG. 7 is an elevational view of the right end of the relay as viewed inFIG. 6.

Referring now to the drawings in detail, and first to FIGS. 1-5 thereof,there is shown a relay including an L-shaped field member or frame 10 ofmagnetizable material. Frame 10 has a pair of mutually perpendicularlegs 11 and 12, leg 11 serving as a support or base on which anelectromagnet 13 is mounted.

Electromagnet 13 includes a core 14 and a coil 15 wound on a bobbin orspool 16, the coil being covered by a layer 17 of insulating material.Core 14 is T-shaped, comprising a body portion 18 and a cross bar orpole piece 19 which is integral with and extends transversely to bodyportion 18 at one end thereof. Body portion 18 has a square transversecross-section and extends through a square axial bore in spool 16 alongthe axis of coil 15. Body portion 18 terminates in an end portion 20, ofreduced cross-section, which extends through a rectangular aperture inleg 11. End portion 20 is upset, as shown in FIG. 4, to cause theshoulder 21, which is formed at the intersection of the end portion andthe body portion, to abut leg 11 and rigidly secure 3,051,804 PatentedAug. 28, 1952 the core thereto so that coil 15 and core 14 are parallelto leg 12.

Although the spool can be mounted in any one of several different ways,it is particularly advantageous to make the spool slightly longer thanthe distance between pole piece 19 and leg 11 and shoulder 21, so thatthe spool is compressed between the pole piece and leg 11 in the finalassembly. Also, the core can be a single piece or, as shown in thedrawing, it advantageously can be of two identical T-shaped punchings 22and 23 disposed in face-to-face contact.

The free end of leg 12 is recessed to provide a pair of parallel ears 24and a bearing edge 25 extending between the ears, the edge beingsuitably bevelled or sharpened to provide a fulcrum or knife edge onwhich the armature 26 is pivoted.

Armature 26 is in the form of an integral magnetic member including aflat body portion 27 which is Wider than leg 12 and has a pair of spacedapertures located adjacent to one end thereof and through which ears 24extend. The length of each of cars 24 is greater than the thickness ofbody portion 27, so that the armature is prevented from moving laterallyof leg 12. Furthermore, the ears and apertures are suitably shaped sothat the armature can pivot about the edge 25, the body portion engagingthe edge along a line which extends between the apertures therein.Armature 26 has a pair of parallel arms or stop tails 28 which extendtransversely to and at one end of body portion 27 along the face of leg12 opposite electromagnet 13. Arms 28 are bent, as indicated at 29, sothat the lower portions thereof are parallel to leg 12 when the armatureis in the position shown in FIG. 1.

A T-shaped bracket 30 is mounted on the side of leg 12 oppositeelectromagnet 13 and is secured thereto by a pair of tabs 31 which arebent into engagement with leg 12 and extend through a pair of notches 32formed in the side edges of the leg. Bracket 30 has a cross bar 33extending transversely of leg 12, tabs 31 being connected to the ends ofthe cross bar and extending outwardly therefrom prior to the bracketbeing secured to the leg, as shown in FIG. 5. Cross bar 33 is parallelto edge 25 but lies closer to the other end of leg 12 than to edge 25,being near base leg 11.

Bracket 30 also includes a shank 34 extending longitudinally of leg 12and through an aperture 35 formed in armature 26. The end of shank 34 isbent, as indicated at 36, and overlies armature 26 to retain thearmature in operative engagement with the frame member. T o accomplishthis, the distance between the end of shank 34- and the adjacent surfaceof the armature, when the armature engages edge 25, is made less thanthe length of cars 24 so that the ears cannot be withdrawn from theircooperating apertures. In other words, the end portion of shank 34limits movement of armature 26 in a direction longitudinally of leg 12.

In some instances, it is desirable to permit the armature to bedisassembled. To accomplish this, bracket 30 can be constructed from arelatively thin, resilient material so that shank 34 can be bent toallow the end portion thereof to pass through aperture 35. Thus,although the armature is normally retained in operative engagement withthe frame member, it can nevertheless be removed.

Bracket 30 also includes a lug 37 which projects from the side of crossbar 33 opposite to that from which shank 34 extends, in a directionperpendicular to leg 12, the lug having a suitable aperture and a groovefor retaining and fastening one hooked end of a restoring spring 38.

Restoring spring 38 is a conventional tension spring having a pair ofend hooks or loops, the lower one of which is attached to lug 37 and theupper one of which passes through aperture 35 and biases the armature ina counterclockwise direction, as viewed in FIG. 1. Spring 38 also exertsa force along a line which is essentially parallel to leg 12 and biasesbody portion 27 towards engagement with edge 25.

Cross bar 33 and arms 28 are arranged to be engageable with each otherso that restoring spring 38 biases the arms into engagement with thecross bar and limits the pivotal movement of the armature in acounterclockwise direction, which direction, as pointed out hereinafter,is away from engagement with the pole face 39 of the pole piece 19. Thebracket is of a nonmagnetic material and accordingly prevents arms 28from sticking to the cross bar and thereby interfering with theoperation of the relay.

Frame 1% core 14 and armature 26 are so dimensioned and assembled that,under ideal circumstances, energization of coil 15, and resultingpivotal movement of the armature about edge 25, will bring the armatureinto flush, face-to-face engagement with the flat pole face 39.Tolerances in the normal manufacturing procedures employed for relaysare such, however, that it often happens that edge 25 and pole face 39are not spaced from frame leg 11' by precisely the same distancesrequired for such flush face-to-face engagement between the armature andthe pole face. If these distances are not precisely correct, the resultis that the body portion 27 of the armature will lie at an angle to poleface 39 when the armature is in fully energized position. Thus, if edge25 is spaced from leg 11 by a greater distance than is pole face 39, thearmature will pivot into engagement with the edge of the pole face mostdistant from edge 25. If, on the other hand, pole face 39 is spaced fromleg 11 by a greater distance than is edge 25, energization of coil 15will cause the armature to pivot into engagement with the edge of thepole face closest to edge 25. In either event, body portion 27 of thearmature lies at an angle to the pole face, when the relay is energized,so that there is an air gap between the pole face and body portion 27which causes a material reduction in the available holding force for thearmature below the maximum value established by the design of the relay.

Such reduction in the armature holding force is more severe when thearmature engages only the edge of the pole face nearest edge 25. This isso because such engagement of the armature and pole face not only causesan air gap but also reduces the effective torque arm through which themagnetic force is applied to the armature.

Obviously, the difficulties just described can be avoided by requiringthat the frame 10, core 14 and armature 26 be made and assembled withabsolute preciseness. This would, however, unduly increase the cost ofmanufacture of the relay. According to the present invention, thepossible losses in holding force applied to the armature are minimizedby minimizing the width of the pole face 39 in the direction of thelongitudinal dimension of body portion 27 of the armature (that is, in adirection at right angles to edge 25). Thus, as will be clear from FIGS.1 and 4, pole face 39 is in the form of a rectangle which isapproximately twice as long as it is wide, the long dimension of therectangle extending parallel to edge 25 and therefore transverse to bodyportion 27. In effect, this configuration of pole face 39 allows thepole face to have a minimum dimension longitudinally of body portion 27and a maximum dimension transversely thereof so that, while the desiredtotal pole face area is provided, the distance between the two edges ofthe pole face which can be contacted by the armature (when flushface-to-face engagement between the armature and the pole face is notachieved) is minimized. Making this critical distance as small aspossible assures that any air gaps existing between the pole face andthe armature, when the relay is energized, will be kept to a 1- minimumand that variations in the effective torque arm through which themagnetic effect of the coil 15 is applied will also be minimized.

The relay also includes a terminal board or front plate 40, of suitableelectrical insulating material, which is secured to an arm 41 of frame10 by a stud 42 and nut 42.. The frame also has a pair of ears 43 whichextend into apertures or recesses 43 suitably formed in terminal board4%. Terminal board 40 extends parallel to leg 12 and coil 15 on the sideof the coil opposite leg 12, arm 11 being paraliel to leg 12.

Terminal board 43 is also provided with a pair of tapered lugs 44, asbest seen in FIG. 3, which provide edge portions for engaging acooperating portion of a cover, indicated by the dotted lines in FIG. 1,to detachably secure the cover which encloses the components of therelay.

A pair of terminals 45 extend through board 40 on opposite sides of themounting stud 42 and are connected electrically to the terminals of thecoil 15. Adjacent the other end of the board 40 are mounted a pluralityof arms 46 which, at their inner ends, each carry a different one of aplurality of the fixed contacts 47 of the relay.

A plurality of movable contacts 48 are mounted each on the end of adifferent one of a plurality of spring arms 49, the contacts beingarranged, as shown, to form a plurality of single pole, double throw,make-break contact assemblies. The other end of each of the spring arms49 extends through a block 50- of insulating material, the block beingmounted on body portion 27 of armature 26 by a mounting plate 51 and apair of rivets 52. The fixed ends of the spring arms 49 are connected toa plurality of flexible conductors which are in turn connected to aplurality of terminals 53 mounted on and projecting through board 40.

FIGS. 6 and 7 illustrate a modification of the terminal board 40 whichpermits the board to be keyed into a suitable supporting member. In thisembodiment, board 48 has an enlarged, quadrangular locator portion 54,through which terminals 46 and 53 extend, and a pair of cylindricallocator projections 55, through which terminals 45 extend. Portion 54and projections 55 extend beyond the edge of the cover, indicated by thedotted lines in FIG. 6, and are adapted to be inserted into similarlyshaped apertures in the supporting member so that the relay can bemounted in only one position. The supporting member can be a channelmember 56, FIG. 6, the base web of which is provided with openings 57and 58 of such shape and size as to snugly accommodate portion 54 andprojections 55, respectively.

In operation, when the relay is de-energized, the restoring spring 38holds armature 26 in the position shown in FIG. 1. In this position,arms or tails 28 engage cross bar 33 and movable contacts 48 engage thenormallyclosed contacts, the spring arms 49 being suitably adjusted toprovide the necessary contact pressure. When the relay is energized, amagnetic field is induced in such manner that the flux passes throughcore 14, frame 10, and armature 26 and there-by attracts the armatureinto engagement with pole face 39. As the armature moves from theposition shown in FIG. 1 into engagement with pole face 39, movablecontacts 48 disengage from the normally-closed fixed contacts and moveinto engagement with the normally-open fixed contacts. The armature isheld in engagement with the pole face 39 so long as the force ofmagnetic attraction exceeds the spring forces acting on the armature.When the relay is de-energized, restoring spring 38 pivots the armatureuntil arms 28 engage the bracket 30, the position of FIG. 1 being thusreestablished.

It will be obvious to those skilled in the art that many changes can bemade in the details and arrangement of the parts shown and describedwithout departing from the scope of the invention as defined in theappended claims.

I claim:

1. In an electromagnetic relay, the combination of a magnetic framemember comprising a flat base, and

a flat leg projecting at right angles from said base and terminating ina free tip presenting a bearing edge spaced from said base;

an electromagnet mounted on said base and extending beside said leg,said electromagnet comprising a core, and

a bobbin-supported coil,

said core being T-shaped and disposed with the stem of the T extendingthrough said coil and the crossbar of said T extending across one end ofthe bobbin supporting the coil, said base being provided with an openingand the end of the stem of the T of said core being mechanically fixedin said opening to rigidly secure said core with said coil being clampedbetween said base and the cross-bar of the T of said core,

the width of the cross-bar of the T of said core being small as comparedto the length thereof and said core being so positioned that the lengthof the crossbar of the T thereof extends parallel to said bearing edge;

an armature of magnetic material, said armature comprising a fiat bodypivotally engaged with said bearing edge and extending from said legbeyond said cross-bar of the T of said core, said armature body beingprovided with an opening disposed at the side of said leg opposite saidelectromagnet;

a generally T-sha-ped, integral nonmagnetic bracket mounted on the sideof said leg opposite said electromagnet, said bracket comprising a stemportion,

a fiat crossbar portion, and

a spring-retaining lug,

said cross-bar portion of said bracket extending transversely of saidleg near said base and said stem portion of said bracket extendinglongitudinally of said leg and projecting through said opening in saidarmature body, the tip of said stem portion being located on the side ofsaid armature body opposite said base and extending at an angle to theplane of said leg to retain said armature body in proper location,

said leg being provided with a pair of transversely opposed notcheslocated each in a different edge thereof, and end portions of saidcross-bar portion of said bracket being bent each into engagement with adifferent one of said notches;

a support secured to said base and projecting therefrom on the side ofsaid electromagnet opposite said a fixed contact mounted on said supportand projecting toward said leg;

movable contact means mounted on said armature body and including aspring arm extending to a point adjacent said fixed contact on the sidethereof facing said base; and

a tension spring having one end connected to said spring-retaining lugand the other end connected to said armature body on the side of saidleg opposite said electromagnet,

said spring being operative to pivot said armature body on said bearingedge in a direction away from said electromagnet to such a degree thatsaid movable contact means is caused to engage said fixed contact,

energization of said electromagnet causing said armature body to pivoton said bearing edge, against the action of said tension spring, intoengagement with the cross-bar of the T of said core.

2. A relay in accordance with claim 1 and wherein said core consists oftwo identical T-shaped punchings dis posed in face-to-face contact witheach other, the stem portion of each of said punchings having a tipdisposed in said opening in said base mechanically deformed to rigidlysecure the punching to said base.

3. A relay in accordance with claim 1 and wherein said armaturecomprises a pair of stop tails integral with said armature body andextending parallel to each other and generally longitudinally of saidleg on the side of said bracket opposite said leg, said tails beingspaced apart transversely of said leg and each having a free tipdisposed to swing into engagement with a different half of the crossbarportion of said bracket when said armature body is pivoted away fromsaid electromagnet, said spring-retaining lug being centered on saidcross-bar portion of said bracket and said tension spring extendingbetween and parallel to said tails,

said stop tails coacting with said cross-bar portion of said bracket tolimit pivotal movement of said armature away from said electromagnet.

4. A relay in accordance with claim 1 and wherein said support is a bodyof insulating material extending from said base to a point materiallybeyond the location of said armature, said body of insulating materialbeing of substantial thickness,

said base of said frame member having a projection located on the sideof said electromagnet opposite said leg and extending parallel to saidleg, said projection engaging the face of said support which is directedtoward said electromagnet and being rigidly secured to said support,said projection being narrower than said base and at least generallycentered with respect to the width of said support,

said support comprising a pair of cylindrical locator projectionsdisposed each on a different side of the location of said projection onsaid base, said locator projections extending away from said support onthe side thereof opposite said electromagnet, the relay comprising apair of connector terminals extending each through a different one ofsaid locator projections.

5. A relay in accordance with claim 4 and further comprising a pluralityof fixed contacts mounted on said support and a plurality of spring armtype movable contact means mounted on said armature body and eachcoacting with corresponding ones of said fixed contacts,

said support further comprising a quadrangular locator projectionextending from the side of said support opposite said electromagnet,said fixed contacts each comprising a supporting arm and all of saidsupporting arms extending through said quadrangular locator projection.

6. In an electromagnetic relay, the combination of a magnetic framemember comprising a flat base, and

a flat leg projecting at right angles from said base and terminating ina free tip presenting a bearing edge spaced from said base;

an electromagnet mounted on said base and extending beside said leg,said electromagnet comprising a core of magnetic material connected atone end to said base and having an exposed pole portion at the otherend, and

a coil surrounding said core between said base and said pole portion;

an armature of magnetic material, said armature comprising a flat bodypivotally engaged with said bearing edge and extending from said legbeyond said pole portion, and

a pair of elongated parallel stop tails integral with said body andprojecting therefrom along the side of said leg opposite saidelectromagnet,

said body having an opening located between said tails;

a generally T-shaped integral nonmagnetic bracket mounted on said leg ofsaid frame, said bracket comprising a stem portion,

a fiat cross-bar portion, and

a spring-retaining lug projecting away from said stem and cross-barportions,

said cross-bar portions extending transversely of said leg near saidbase and being disposed in face-to-face contact with said leg, and saidstem portion extending longitudinally of said leg and through saidopening in said armature body, the tip of said stem portion beinglocated on the side of said armature body opposite said base andprojecting at an angle to the plane of said leg to retain said armaturebody in proper location,

said frame leg being provided with a pair of trans versely opposednotches located each in a difierent edge thereof and end portions ofsaid cross-bar portion being bent each into engagement with a differentone of said notches,

said stop tails extending to a location adjacent said cross-bar portionand each being disposed to swing into engagement with a different halfof said crossbar portion when said armature body is pivoted away fromsaid pole portion;

a support secured to said base on the side of said electromagnetopposite said leg;

21 pair of fixed contacts mounted on said support and spaced apart inthe direction of movement of said armature body;

movable contact means mounted on said armature body and including aspring arm projecting between said fixed contacts; and

a tension spring having one end connected to said spring-retaining lugand the other end connected to said armature, said spring extendingbetween and parallel to said stop tails,

energization of said electromagnet causing said armature body to pivoton said bearing edge toward said pole portion and thereby causing saidmovable contact means to engage the one of said fixed contacts nearestsaid base,

said tension spring being effective, when said electromagnet isdeenergized, to cause said armature body to pivot on said bearing edgeaway from said pole portion and thereby cause said movable contact meansto engage the one of said fixed contacts most distant from said base,such pivotal movement of said armature body causing said stop tails toswing toward said frame leg and said cross-bar portion of said bracketserving to prevent magnetic sticking of said tails to said frame leg,

said stop tails coacting with said cross-bar portion of said bracket tolimit pivotal movement of said armature in a direction away from saidelectromagnet.

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